This invention relates to a catheter balloon and a balloon catheter using the same balloon, more specifically to a balloon for being attached to a catheter and used to dilate a stenosed part of a tubular organ such as a blood vessel and a balloon catheter using the same balloon, especially a blood vessel-dilating catheter.
In recent years, dilatation of a diseased part (stenosed or occluded part) in coronary artery by a catheter equipped with a balloon (blood vessel-dilating catheter) is more and more widely used as a method of treating cardiac infarction and angina pectoris.
A blood vessel-dilating catheter generally consists of a tubular catheter body, a dilating balloon attached to the distal end portion of the tubular catheter body, and a hub attached to the proximal end of the tubular catheter body.
For the material for the dilating balloon, polyolefin, polyethylene terephthalate (PET), polyamide, for example, are used.
Of polyolefin, low-density polyethylene (LPDE), high-density polyethylene (HDPE), straight-chain low-density polyethylene(LLDPE), and ethylene-vinyl acetate copolymer are used.
Although a balloon made of an olefin has a good flexibility and can be welded to the tubular catheter body, the resistance to internal pressure is comparatively small, and the change of diameter against a change of inflating pressure (compliance) is large.
A balloon made of PET generally has a high strength, and hence a high resistance to internal pressure and a small compliance. However, the balloon is stiffs, and the tracking capability (capability of a balloon to advance along flexures in a tubular organ) is low. If the wall of the balloon is made thin so as to increase the tracking capability, the resistance to internal pressure becomes low, and the balloon becomes pinhole prone.
A balloon made of a nylon or a polyamide has intermediate properties between the properties of a balloon made of a polyolefin and those of a balloon made of PET. If the wall of this balloon is made thin, the balloon becomes pinhole prone. If the wall of this balloon is made thick, on the other hand, the tracking capability becomes inadequate.
To solve these problems with conventional catheter balloons, especially a catheter balloon made of PET, a multilayer balloon made of PET as the base layer and polyethylene or other plastic for an additional layer is disclosed in Patent Application Lay-open Gazette No. 1991-205064 and Patent Application Publication Gazette No. 1994-507101. These balloons were proposed in order to improve the weldability of a balloon made of PET to a tubular catheter body or to increase the resistance to pinholes. To increase the flexibility and the strength of the balloon simultaneously is not intended.
In the balloons disclosed in the above gazettes, the PET layer must be thick to obtain a balloon with a high strength (resistance to internal pressure), the balloon becomes stiff and the tracking capability of the balloon decreases If the PET layer is made thin to obtain a flexible balloon, the strength of the balloon decreases and the balloon becomes pinhole prone.
The object of this invention is to provide a new improved balloon which has an adequate strength (resistance to internal pressure) and is flexible enough to give a satisfactory tracking capability.